Answer

Note: The general guidelines outlined here can be used for older DSM editions as well, including the DSM-IV-TR

You should cite the DSM as a reference book, as directed on pages 204-205 of the APA Manual. If you are using the online version of the DSM then you would want to follow the guidelines on p. 205, example 29, of the manual.

For a reference work you will also want to cite the editor(s). With the DSM that is a little odd since they lump the editors in with the task force members that helped write the book and there is a good case for citing the work as having a corporate author: the American Psychiatric Association.

Lead with APA as author

In text

Format your in text citation as follows: (American Psychiatric Association, 2013) or ("Avoidant personality disorder," 2013). If quoting, be sure to include the page number(s) for your quote. If you will be citing the APA multiple times in-text, and are using an author lead in your reference list, you should list the first citation as (American Psychiatric Association [APA], 2013) and all subsequent entries as (APA, 2013).